WO-A1-85/05553 discloses bacterial cell surface proteins having fibronectin, fibrinogen, collagen, and/or laminin binding ability. Thereby it is shown that different bacteria have an ability to bind to fibronectin, fibrinogen, collagen, and/or laminin. It is further shown that fibronectin binding protein has a molecular weight of 165 kD and/or 87 kD, whereby it is probable that the smaller protein is a part of the larger one.
Fibronectin is a large glycoprotein (M.sub.r ca 450 kd) with two similar subunits, which may vary in moleclar size depending on a complex splicing pattern of a precursor mRNA (1). The major function of fibronectin, which is found in body fluids, blood clots and extracellular matrices, seems to be related to the ability of the protein to mediate substrate adhesion of most eukaryotic cells (2, 3, 4, 5.)
In the late seventies, Kuusela found that fibronectin not only interacts with eucaryotic cells but also binds to cells of Staphylococcus aureus (6). Since this observation, a number of pathogenic microorganisms have been shown to bind to fibronectin with a high degree of specificity and a high (7). Fibronectin in the extracellular matrix appears to serve as a substratum also for the adhesion of different microorganism The binding of fibronectin may for some microorganisms represent a crucial step in the colonization of host tissue and development of infection.
Several different cell surface components have been implicated as fibronectin receptors on Gram-positive bacteria including lipotechioc acid (8, 9) and protein (10). In previous studies a fibronectin binding protein with a M.sub.r of 197-210 kD has been isolated from S. aureus strain Newman (11, 12) and tentatively identified as a fibronectin receptor. To further characterize this fibronectin binding protein from S aureus, the gene for this protein has been cloned in E. coli. The fibronectin binding domain with in this protein has also been localized and the behaviour of a fusin protein containing this domain and IgG-binding regions of protein A will be disclosed below.